Like the Joker said, “If you are good at something, then never do it for free.” Spread your knowledge to your co-students. You can charge by the hour or every week. You can do it from your place or travel to others’ homes.
Or, you can also teach over the internet, which is basically the biggest thing trending and needed right now. This is not only a great way to make money while studying abroad but also the best form of social service. You not only enhance your knowledge about the subject you love, but you also imbibe more passion into the chosen subject.